The natural lens of an eye is a lenticular-shaped body having three portions. The core portion is the nucleus which is surrounded by a cortex. Enclosing the cortex and constituting the wall of the lens is the capsule. The degenerating or degenerated lens of an eye, or a localized point of degeneration within a lens is referred to as a cataract. As a result of a cataractous degeneration, the lens becomes opaque resulting in visual disability.
Numerous surgical procedures have been developed for removal of cataracted lenses including intracapsular extraction and extracapsular extraction. When the cataract is removed without breaking the capsule, such that the lens is entirely removed, an intracapsular extraction is performed. By contrast, when the forward facing, anterior portion of the capsule is removed followed by separate removal of the lens contents, an extracapsular extraction is performed. Generally, in an extracapsular extraction, the posterior portion of the lens capsule remains in the eye.
In extracapsular cataract extraction, an incision is made into the eye, and the anterior capsule is removed. The size of the nucleus dictates the size of the incision which must be made for the cataract to be extracted. Since the nucleus may be large in diameter for example, approximately 10 millimeters, an incision of 10.5 millimeters to 12 millimeters is employed with this technique. However, a smaller incision would present advantages with respect to reducing operative time, increasing post-operative wound strength, quickening healing and reducing the frequency of bleeding and infection complications. Therefore, techniques have been developed to minimize the diameter of the incision made into the eye for cataract removal. One such technique and instrument developed is described and claimed in U.S. Pat. No. 4,538,611, issued to Charles Kelman on Sept. 3, 1985 and entitled "Surgical Instrument and Method of Cutting a Lens of An Eye". An additional process is described in U.S. Pat. No. 4,732,150, issued to Gerald Keener, Jr. on Mar. 22, 1988 and entitled "Process for Cataract Extraction". In both these methods, a small incision is made into the eye and an instrument is inserted therethrough for cutting the lens into multiple sections so that smaller sections of the lens can be removed through the incision rather than the entire lens. The lens nucleus is moved into the anterior chamber of the eye and is cut into multiple sections prior to removing the individual sections through the incision. Such procedures and instruments; however, require that the lens be moved to the anterior chamber of the eye. The lens and the multiple sections cut from the lens may contact the corneal endothelium of the eye resulting in damage to this tissue.
A need has thus arisen for an ophthalmic surgical instrument and method for removing a lens of an eye while in the posterior chamber of the eye to thereby minimize any damage to the endothelium layer of the eye. In such a procedure, containment of the lens and cut portions of the lens must be accomplished within the posterior chamber prior to removal through the incision made in the eye.